The present invention relates to an electronic device rendering it possible to store logic a representation of a state of a process capable of successively assuming different possible states.
Protected access memories are known, whose principal object is to store secret or confidential data. In these memories, access is controlled by means of specialized access control logic interposed between the memory and the external surroundings. One embodiment of such access logic is disclosed in commonly-assigned Ugon U.S. Pat. No. 4,211,919 entitled "PORTABLE DATA CARRIER INCLUDING A MICROPROCESSOR". In the Ugon data carrier, the access logic is implemented by means of a microprocessor, access being obtained upon presentation of a correct password.
In many applications, it is necessary to store the number of mistakes, the number of illegal access actions or of the appearance of illegal occurrences. In the best known embodiments, the normal manner of recording such events comprises recording them in a permanent memory or in counting these by means of specialized counters making use of electrically erasable memories. A description of these devices is given in commonly-assigned U.S. patent application Ser. No. 137,973, filed Apr. 7, 1980, by Michel UGON, and entitled "DEVICE FOR THE PROTECTION OF ACCESS TO A PERMANENT MEMORY OF PORTABLE DATA CARRIER" now U.S. Pat. No. 4,295,041.
This method has at least three disadvantages. Firstly, it requires space in the principal memory. Secondly, the counting capacity is limited to the maximum capacity of the counter and cannot be modified even if space remains available in the memory. Finally the number of events recorded in the permanent memories can neither be reduced nor erased.